1. Field of the Invention
The present invention relates to a brass-plated steel wire for reinforcement of rubber articles such as tires, industrial belts and the like, a method of manufacturing the wire, and a steel cord consisting of the wires twisted together, particularly aims to improve initial adhesion of the steel wire to rubber. Here, the initial adhesion means adhesion of steel wire to rubber at the initial stage of vulcanization when manufacturing rubber articles.
2. Related Art
In steel wire or steel cord consisting of wires twisted together used for reinforcement of rubber articles, good adhesion to rubber is required to obtain reinforcing effect. On improvement of the adhesion in steel wire or steel cord with brass-plating, it has been widely known that the adhesion can be more increased by appropriately determining Cz/Zn ratio of the brass plating, thickness of the brass plating and the like.
Moreover, Japanese Patent Application Laid-open No. SHO 62-23977 proposes a method of improving adhesion by applying copper and zinc plating to steel wire, then alloying the copper and zinc to form brass plating by thermal diffusion, and thereafter quenching the brass-plated steel wire with water, thereby controlling production of zinc oxide on the surface of wire.
Further, Japanese Patent Application Laid-open No. SHO 63-33135 proposes to mitigate deterioration of adhesion after steam aging by containing not less than 4 mg/m.sup.2 of phosphorous in the brass plating of brass-plated steel wire.
However, in a method comprising quenching with water immediately after thermal diffusion as disclosed in the above Japanese Patent Application Laid-open No. SHO 62-23977, a quenching device is necessary, and also a dryer is necessary for preventing production of rust, so as to require places for setting these devices. As a result, it becomes difficult to produce a steel wire economically.
Moreover, in a steel wire containing phosphorous in the brass plating as disclosed in the above Japanese Patent Application Laid-open No. SHO 63-33135, adhesion to rubber after steam aging is improved, but adhesion at the initial stage of vulcanization is not sufficient to achieve economical production of rubber articles with shortened curing time for energy saving.
Furthermore, in case of manufacturing a cord consisting of steel wires having slightly different diameters, it takes a time to change drawing die schedule in ordinary wet drawing process.
An object of the present invention is to provide economical way to improve initial adhesion of steel wire or steel cord for reinforcement of rubber articles and to materialize shortening of curing time, thereby enabling economical production of rubber articles.